Combustible moistureproof percussion primer

ABSTRACT

A percussion primer for initiating firing of a cartridge which is fully combustible and which is impervious to moisture vapor. The primer mix is contained in a consumable moistureproof sealed cup-shaped closed member received in a molded propellant support and backed against a molded propellant anvil which function together as a unit attachable to a cartridge.

0 United States Patent [151 3,645,207

Daniels Feb. 29, 1972 [54] COMBUSTIBLE MOISTUREPROOF 3,169,483 2/1965Gawlick et a]. ..102/45 X PERCUSSION PRIMER 3,236,181 2/1966 Woodring etai..

3,320,887 5/1967 Quinlan et al. [72] Edward Clmm Ohm 3,336,871 8/1967Quinlan ..l02/38 [73] Assignee: TRW Inc., Cleveland, Ohio PrimaryExaminerR0bert F. Stahl [22] Ffled' May 1969 Attorneyl lill, Sherman,Meroni, Gross & Simpson [21] Appl. No.: 822,238

[57] ABSTRACT [52] US. Cl. ..l02/40, 102/DIG. 1, 102/45 A percussionprimer f initiating fi i f a cartridge which is [51] I Cl V "F42b 5/18F42b 9/08 fully combustible and which is impervious to moisture vapor.[58] Fleld of Search ..102/38, DIG. l, 43, 44, 45 The primer mix iscontained i a consumable moistureproof sealed cup-shaped closed memberreceived in a molded [56] References (med propellant support and backedagainst a molded propellant UNTED STATES PATENTS anvil which functiontogether as a unit attachable to a cartridge. 740,790 10/1903 Young eta1. ..102/45 1,353,1 18 9/ 1920 Thompson 102/38 5 Claims, 3 DrawingFigures COMBUSTIBLE MOISTUREPROOF PERCUSSION PRIMER BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to percussionprimers and more particularly to a moistureproof fully combustibleprimer. The invention herein described was made under a United StatesDepartment of the Army contract.

2. Prior Art Recent developments in ammunition construction andcartridge firing weaponry have made possible the use of caselesscartridges which are constructed primarily of molded propellant with aprojectile attached thereto. Such cartridges have the advantage of beingfully combustible whereby the need for a cartridge case is eliminated.

In prior art cartridges involving metallic cartridge cases, the primerusually consisted of a metal-ended percussion cap in the case ofcenter-fired cartridges. Because of the necessity for ejecting thecasing from the weapon after firing and because of the mositureproofnature of the metal casing itself, such metal-ended primers workedadequately. However, metal primers cannot be adapted for use incartridges which are either constructed entirely of propellant or whichare constructed of some casing material which is fully combustible ormeltable and which contains the propellant. In such instances the use ofmetal-ended primers would destroy some of the advantages derived fromfully combustible cartridges in that the primer would have to be ejectedor otherwise removed from the weapon after firing.

The use of molded propellant as a cartridge and as a container for thesensitive priming mix, which would then be fully combusted, may overcomethis disadvantage. However, priming mix is adversely affected bymoisture. Military requirements as well as general usage dictate thatthe cartridge be reliably functional after exposure to moisture.Therefore, the use of molded propellant to contain the priming mix isunsatisfactory inasmuch as it would not protect the mix from moistureand the primer would be subject to failure after exposure to suchmoisture.

SUMMARY OF THE INVENTION The disadvantages of the prior art are overcomeby the instant invention which provides an hermetically sealed primermix which is percussion exploded.

The primer mix, which may be of any standard type, is contained in anopen-ended cup which, in the preferred embodiment, has an out-turnedflange adjacent the open end. A plate is used to close the cup. Both theclosure plate and the cup are constructed of a material which isconsumed during the firing cycle of the cartridge.

A propellant support is provided to receive the cup and closure. Thesupport has a bore therethrough which has a reduced diameter at one endthereof. The cup is received in the reduced diameter portion having itsbottom wall lying in the same plane as the bottom of the support and itsflange bottoming on the radial wall of the bore created by the reduceddiameter. A propellant anvil which has the same diameter as the largediameter portion of the bore, is received therein to overlie the closureplate and cup. The anvil has an axial dimension so that its axial endlies in substantially the same plane as the adjacent axial end of thesupport. The elements may then be bonded together to provide a primerassembly which is self-contained and in which the primer mix ishermetically sealed and is impervious to moisture vapor. The assembly isthen adapted to be attached to the base of a cartridge. Because thesupport and anvil are constructed of propellant and because the cup andclosure plate are constructed of a material which is either consumed ordissipated during the firing of the cartridge, the entire primerassembly will be consumed during the firing of the cartridge.

It is then an object of this invention to provide a new cartridgeprimer.

It is a further object of this invention to provide a fully combustibleprimer wherein the primer mix is hermetically sealed against elementaldegradation.

It is yet another object of this invention to provide a primer assemblyhaving a primer mix hermetically sealed in a cupshaped housing closed bya closure plate, the housing and plate constructed of a material whichis dissipated during the firing cycle.

It is yet another and more specific object of this invention to providea primer assembly wherein the primer mix is hermetically sealed in ahousing which is received in a propellant support and which bottomsagainst a propellant anvil; the support, anvil, housing and mix alladapted to be consumed during during the cycle of a cartridge with whichthe primer is associated.

Other and further objects of this invention will be apparent to thoseskilled in this art from the following detailed description of theannexed sheet of drawings which, by way of a preferred embodiment of theinvention, illustrate one example of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of acartridge equipped with the primer of this invention.

FIG. 2 is an enlarged fragmentary cross-sectional view of a base portionof the cartridge of FIG. 1 illustrating the primer assembly of thisinvention.

FIG. 3 is an end plan view of a modification of the primer of thisinvention illustrating underlying portions by broken lines.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a cross-sectionalrepresentation of one form of a caseless cartridge equipped with aprimer assembly according to this invention. The cartridge 10 includes apropellant sec tion 11 and a projectile 12. The propellant section 1 1consists of a tubular molded propellant body 11a having a base plug 13inserted in one end thereof and the projectile 12 inserted in the otherend and projecting therefrom. The base member 13 is also constructed ofpropellant and includes an axial fire bore 14 therethrough having anincreased diameter portion 15 at its axially outer or base end. The firebore 14 except for the increased diameter portion l5 contains anignition charge and the remainder of the central area of the tubularbody 11a is filled with propellant grains 16. The increased-diameterportion 15 of the fire tube 14 contains the primer assembly of thisinvention 20 therein.

Although the invention is described as being used in connection with aspecific caseless cartridge, it is to be understood that this inventionmay be used with any cartridge whether it is constructed of moldedpropellant, a single grain of propellant, a consumable case cartridge,or a standard metal or plastic case cartridge. It is to be furtherunderstood that the primer assembly of this invention is adapted to actas an initial igniter of a main charge and that its use need not berestricted to ammunition.

FIG. 2 illustrates the primer assembly of this invention in across-sectional view. The assembly 20 consists of a primer mix 21received in a combustible cup-shaped housing 22 which has an out-turnedflange 23 adjacent the open end thereof. The open end of the cup 22 isclosed by a closure plate 24. The cup and closure plate are attachedtogether in a manner which will prevent entrance of moisture betweenthem into the interior of the cup. They therefore form amoisture-impervious housing. The cup 22 is received in areduced-diameter portion 25 of an axial bore 26 through a support member27 with the out-turned flange 23 thereof bottoming against a radialledge 28 formed by the reduced diameter inner diameter 25 of the bore26. An anvil 29 closes the major diameter portion of the bore 26.

In the preferred embodiment, the support 27 is disc-shaped, having thebore 26 extending along its axis with the reduced diameter portion 25open to a front end 30 of the support 27.

The cup 22 is circular and the distance from the flange 23 to the bottomwall 31 of the cup is such that when the cup is received in the reduceddiameter portion 25, the bottom wall 31 is coplanar with the wall 30 ofthe support. Preferably, the cup 22 has a diameter equal to the diameterof the portion 25 of the bore 26 so that the cup is snugly received inthe support. The closure plate 24 and the flange 23 have a diameterequal to the major diameter of the bore 26 as does the anvil 29 so thatthe entire assembly is radially stable. The anvil 29 has an axial lengthsuch that its axially outer end 33 lies in the same radial plane as theend 34 of the support 27. In order to further hold the assembly in itsassembled condition, the anvil 29 may be adhesively retained in the bore26.

Thus, the primer assembly can be handled as a single piece having a discconfiguration susceptible to mass manufacturing within relatively closetolerance limits. The assembly is then adapted to be received in thebase of a cartridge in a recessed area therein such as the increaseddiameter portion 15 of the bore 14 illustrated in FIG. 1 wherein it willbottom on the ledge 37 created by the increased diameter. Preferablywhen assembled in the cartridge the primer assembly lies flush with thebase.

The support 27 and anvil 29 may be formed of molded propellant or may beformed of a cast or machined structure of a large grain of propellant. Atypical molded propellant composition which may be used in forming theanvil and support consists of:

Percent Nitrocellulose 77.45 Nitroglycerin 19.50 Barium nitrate L40Potassium nitrate 0.75 Ethyl centralitc 0.60 Graphite 0.30

This composition has a burning rate within the limits desired inallocated time for combustion.

The cup 22 and closure plate 24 may be constructed of any material whichis either combusted, consumed or otherwise destroyed during the firingcycle of the cartridge and which is impervious to moisture vapor.

The cup and closure may adequately be formed of a plastic film such as anitrate ester which is combustible or may be formed of a reactive or lowmelting point metal which would be fully dissipated during the firingcycle of the cartridge.

The primer mix 21 may consist of any explosive mixture which can bedetonated by percussion. The assembly is adapted, in the preferredembodiment illustrated, to be used in connection with center fireweapons where the firing pin will strike the bottom wall 31 of the cupcompressing the primer mix 21 between the pin and the anvil 29. Anacceptable primer mix for such uses is as follows:

Percent Lead styphnatc 36 Tctracene l2 Barium nitrate 22 Lead dioxide 9Antimony sulfide 7 Zirconium 9 PETN Entrapment of the primer mix betweena firing pin and the anvil will then serve to ignite the primer mixwhich in turn will either combust or otherwise consume a portion of thecup and closure plate sufficient to ignite the propellant material ofthe support and anvil. The entirety of the cup and closure are thencombusted or otherwise consumed during the burning of the support,anvil, and remainder of the cartridge. The flame from the primer mixwill touch off the ignition charge to fire the cartridge.

FIG. 3 illustrates a modification of the primer of this invention. Inthe modification, the anvil member 29b is semirectan ular havin curvedends 38 and 39 mating with the inner rameter wa l of the ma or diameterportion of the bore 26 of the support member 27. The modified anvil 29has a width less than the diameter of the cup 22. in this manner, theflame from the primer mix can extend past the sides of the anvil totouch off the ignition charge in the fire tube 14. Because the anvil hasa major axis length the same as the major diameter of the bore 26, itwill be retained therein in the same manner as the anvil 29. Thus, aunitary assembly is again provided.

It can therefore be seen from the above that my invention provides apercussion primer assembly constructed entirely of consumable materialswhich are destroyed during the firing cycle and in which the primer mixis hermetically sealed against moisture or other environmentalconditions which would adversely affect its ability to detonate.

Although I have herein set forth my invention with respect to certainspecific principles and details thereof, it will be understood thatthese may be varied without departing from the spirit and scope of theinvention as set forth in the hereunto appended claims.

I claim as my invention:

1. A percussion primer assembly comprising: a support member, a borethrough said support member, said bore having a reduced-diameter end, acup-shaped housing member having an open end with an out-turned flangetherearound, said housing member received in the said reduced diameterend of the said support member bore with the said flange received in thesaid nonreduced diameter portion of the said bore bottoming against thereduced diameter portion, a closure member in said nonreduced diameterportion overlying said flanged end closing said housing, said housingcontaining an explosive primer mix, an anvil member received in saidnonreduced diameter portion of said bore closing said bore at one endthereof and entrapping said closure member and housing therein, saidsupport member and said anvil member constructed of a combustiblepropellant, said housing and said closure plate constructed of amaterial impervious to moisture whereby the said primer mix is sealedagainst moisture in said housing, and said housing and said closureplate constructed of a consumable material whereby the entirety of theassembly is destroyed during firing.

2. The assembly of claim 1 wherein the said housing and the said closureplate are constructed of a combustible material impervious to moisture.

3. The assembly of claim 1 wherein the said housing and said closuremeans are constructed of a low melting point metal.

4. The assembly of claim 1 wherein the said housing and said closuremeans are constructed of a nitrate ester.

5. The assembly of claim 1 wherein the entire assembly is disc-shapedhaving atop and bottom axial end, said bore lying generally along theaxis of said disc, said reduced diameter portion open to said top end,the nonreduced diameter portion open to said bottom end, the bottom wallof said cupshaped housing terminating in a plane substantially equal tothe plane of the said top end, said anvil terminating in a planesubstantially equal to the plane of said bottom end, said housing, saidclosure and said anvil substantially filling said bore.

1. A percussion primer assembly comprising: a support member, a borethrough said support member, said bore having a reduceddiameter end, acup-shaped housing member having an open end with an out-turned flangetherearound, said housing member received in the said reduced diameterend of the said support member bore with the said flange received in thesaid nonreduced diameter portion of the said bore bottoming against thereduced diameter portion, a closure member in said nonreduced diameterportion overlying said flanged end closing said housing, said housingcontaining an explosive primer mix, an anvil member received in saidnonreduced diameter portion of said bore closing said bore at one endthereof and entrapping said closure member and housing therein, saidsupport member and said anvil member constructed of a combustiblepropellant, said housing and said closure plate constructed of amaterial impervious to moisture whereby the said primer mix is sealedagainst moisture in said housing, and said housing and said closureplate constructed of a consumable material whereby the entirety of theassembly is destroyed during firing.
 2. The assembly of claim 1 whereinthe said housing and the said closure plate are constructed of acombustible material impervious to moisture.
 3. The assembly of claim 1wherein the said housing and said closure means are constructed of a lowmelting point metal.
 4. The assembly of claim 1 wherein the said housingand said closure means are constructed of a nitrate ester.
 5. Theassembly of claim 1 wherein the entire assembly is disc-shaped having atop and bottom axial end, said bore lying generally along the axis ofsaid disc, said reduced diameter portion open to said top end, thenonreduced diameter portion open to said bottom end, the bottom wall ofsaid cup-shaped housing terminating in a plane substantially equal tothe plane of the said top end, said anvil terminating in a planesubstantially equal to the plane of said bottom end, said housing, saidclosure and said anvil substantially filling said bore.